White Space: Broadcasters Ready for Tests

The FCC—after a delay of several hours Tuesday—approved the plan touted by Google and Chairman Kevin Martin opening up the DTV white spaces to unlicensed devices.

Now, broadcasters get to fight to minimize the interference that the future devices will cause once they are unleashed onto the airwaves.

The orders (outlined last month by Martin but not immediately released) would allow unlicensed devices on unused DTV channels, including adjacent channels, at power levels close to those proposed by Google and other white space boosters.

In a statement, the commission called the plan “a careful first step” with “numerous safeguards” against interference to incumbent users. Martin said the tests by the FCC Office of Engineering and Technology were “an extraordinary step” of testing “to prove the concept that white space devices could be safely deployed”—a conclusion strongly disputed by broadcasters.

Under the plan, devices would be allowed to operate if they use spectrum-sensing technology and geolocation databases to detect and avoid DTV channels and to protect certain sensitive sites like cable head-ends. Devices would be allowed to use just spectrum-sensing technology if they can show to the FCC that it actually works. So far, the spectrum-sensing abilities of prototype devices have had mixed results, and broadcasters have slammed the technology as unreliable.

“Even the FCC cannot compromise the laws of physics,” the Association for Maximum Service Television said in a statement.

MSTV has also taken issue with the FCC’s own peer review of the tests done by the Office of Engineering and Technology. An OET engineering report on the tests, released Oct. 15, claims the OET tests provided “proof of concept” of spectrum-sensing technology—a notion not borne out in the OET’s actual test results, according to broadcasters, and not mentioned in an FCC peer review report Oct. 1. MSTV has filed a Freedom of Information Act request to try to learn when the “proof of concept” was first asserted.

The plan would let portable devices that use both spectrum-sensing technology and geolocation databases to prevent interference to DTV would be limited to 100 mW of power, or 40 mW when operating on channels adjacent to active DTV channels. Spectrum-sensing-only devices—if they can prove viability at the OET—would be limited to 50 mW, or 40 mW on adjacent channels—a level MSTV has said would “eviscerate” DTV in some areas.

Under the Martin plan, fixed devices would operate at a maximum of 4 W, and not at all on adjacent channels unless they can show to the OET that they can avoid interfering with DTV. MSTV wants no fixed devices on the adjacent channels and portable devices at just 5 mW on those channels and 10 mW on the other channels.

To protect the thousands of incumbent wireless mic users, the new white plan space regime will rely on spectrum-sensing technology along with a geolocation database for large events.

But spectrum-sensing, to wireless mic maker Shure Inc., is a non-starter.

“Test data from microphone tests is less favorable to sensing than the DTV data, but gets buried at the back of the report,” Shure told the FCC in its filing in support of a fresh comment period on the data. “It is also heavily redacted. Individual tests are not published.”

Shure says the OET failed to make a case that the future white space devices would not interfere with wireless mic use.

“While not unexpected, today’s FCC decision will greatly complicate the lives of wireless microphone users across the United States and negatively affect tens of millions of Americans listening to live and broadcast events,” Mark Brunner, Shure senior director for global public and industry relations, said in a statement.

Shure had offered its own plan for protecting wireless mics. It would designate “minimally sufficient protected channels” centered around Channel 37 and Channel 11, with all new white space devices managed by a geolocation database that would reflect events, such as sports, that involve abundant mic use. The Shure plan also called for six protected UHF channels (reduced to four channels after three years) and two protected VHF channels, for smaller operations.

But relying in many case on spectrum-sensing alone—as envisioned by the FCC order—will remain problematic.

The order “is a good example of an item that, while very controversial, is going to be critical in providing an opportunity to be building out broadband services and be able to use spectrum in a much more efficient way,” Martin told reporters waiting for the delayed meeting to start Tuesday. “I think that the commission has been studying this for a long time, we’ve done a whole series of testing. ... I think in the end the commission has to balance the competing interests and determine how we try to ensure that there’s not going to be harmful interference to broadcasters but at the same time make sure that we’re utilizing what’s a very valuable national asset in terms of spectrum.”